Conventionally, as a lens drive device for driving a photographing lens of a camera which is mounted on a cellular phone or the like, the present applicant has previously proposed a lens drive device which is provided with a movable body holding a plurality of lenses and being moved in an optical axis direction, a fixed body movably holding the movable body in the optical axis direction, and a drive mechanism for driving the movable body in the optical axis direction (see, for example, Japanese Patent Laid-Open No. 2010-217467). The lens drive device described in the Patent Literature is formed in a substantially rectangular prism shape.
In the lens drive device, the drive mechanism is provided with four drive magnets formed in a substantially triangular prism shape and four drive coils which are wound around in a substantially triangular tube-like shape. The drive magnet is structured of two drive magnet pieces and a magnetic plate. The two drive magnet pieces and the magnetic plate are fixed to each other so that the magnetic plate is sandwiched by the two drive magnet pieces in an optical axis direction. The two drive magnet pieces and the magnetic plate are fixed to each other with an adhesive. The two drive magnet pieces are magnetized so that magnetic poles of opposing faces of the two drive magnet pieces which face each other through the magnetic plate are the same magnetic pole.
Further, the drive magnet is disposed at four corners of the lens drive device and one end face of the drive magnet in the optical axis direction is fixed to a cover member structuring the fixed body with an adhesive. Further, a magnetic piece is fixed to the other end face of the drive magnet in the optical axis direction with an adhesive. The drive coil is fixed to the movable body so that an outer peripheral face of the drive magnet and an inner peripheral face of the drive coil are faced each other through a predetermined gap space.
In recent years, in a market of a camera which is mounted on a cellular phone or the like, the requirement for reducing the size of the camera has been further increased and, in order to meet the requirement, the requirement for reducing the size of a lens drive device used in the camera has been also increased. In the lens drive device described in the above-mentioned Patent Literature, in order to further reduce the size of the device, the drive magnet and the drive coil are required to be small. On the other hand, when the drive magnet and the drive coil are small, a drive force of the drive mechanism for driving the movable body is lowered and thus a gap space between the drive magnet and the drive coil is required to be narrow for preventing lowering of the drive force of the drive mechanism.
In a case that a gap space between the drive magnet and the drive coil is set to be narrow, when the gap space is not formed with a high degree of accuracy, the fixed body to which the drive magnet is fixed and the movable body to which the drive coil is fixed may be interfered with each other to cause a problem in movement of the movable body. However, in the lens drive device described in the above-mentioned Patent Literature, since two drive magnet pieces and a magnetic plate are fixed to each other with an adhesive, in a case that the size of the drive magnet is reduced, the adhesive may be protruded from a space between the drive magnet piece and the magnetic plate unless a coating amount and an applied position of the adhesive are strictly controlled. Therefore, in the above-mentioned lens drive device, when a gap space between the drive magnet and the drive coil is set to be narrow with downsizing of the drive magnet and the drive coil, a problem may occur in movement of the movable body due to the adhesive which is protruded from a space between the drive magnet piece and the magnetic plate.